We think that the support of data deletion from the blockchain side is equally important for many other blockchain applications targeting European market, that's why the whitepaper. Ideally we would like to have the built-in support for the deletion feature in the "official" HL implementation.
The whitepaper describes the deletion feature using Bitcoin protocol as an example because we want to target wide enough audience, but translation to the fabric is obvious. Hopefully it is obvious enough for the cases of Sawtooth Lake and Iroha too, but unfortunately I am not so familiar with them.
So, as the mailing list name suggests, please discuss.